To assess the relationship between apathy and olfaction in patients with early Parkinson’s disease (PD).

Odors can consistently precipitate specific emotions. Apathy and olfactory dysfunction share anatomical pathways. This posits a potential novel therapeutic approach for apathy.

We analyzed data on patients enrolled within 2 years of motor symptom onset in the Parkinson’s Progression Markers Initiative (PPMI) study. Hyposmia was defined as a University of Pennsylvania Smell Identification Test (UPSIT) score at or below the 10th percentile by age and gender. Apathy was identified using the UPDRS part 1A item 1.5. Odds ratios were calculated between apathy and olfaction groups using ANOVA and Chi Square test. Kaplan-Meier curve grouped by olfaction and Log Rank test was used to compare length of time until the onset of apathy. Patients with apathy at the first visit or only had one visit were excluded from this analysis. Cox regression analysis was conducted with apathy as the outcome. Data used in the preparation of this article were obtained from the PPMI database (). For up-to-date information, visit 

Unlike in clinical Alzheimer’s disease and mild cognitive impairment where such an association has been indicated, persons with PD and hyposmia do not have a greater prevalence or risk of apathy, compared to those without. This further highlights the clinical heterogeneity in neurodegenerative disorders. These data argue against this approach as a potential therapeutic modality against apathy in PD.